Could weight-loss drugs eat the world?

From The Economist

The gila monster is a poisonous North American lizard that measures around 50 centimetres and sports a distinctive coat of black and orange scales. This lethargic reptile, which mostly dwells underground and eats just three to four times a year, is the unlikely inspiration for one of pharma’s biggest blockbusters: a new generation of weight-loss drugs that has patients—and investors—in a frenzy. Originally made for diabetes, evidence is growing that they also have benefits in diseases of the heart, kidney, liver and beyond.

Since the late 1980s scientists believed that a gut hormone called glucagon-like peptide-1 (glp-1), which is secreted by the intestines after a meal, could help treat diabetes. glp-1 increases the production of insulin (a hormone that lowers blood-sugar levels) and reduces the production of glucagon (which increases blood-sugar levels). But glp-1 is broken down by enzymes in the body very quickly, so it sticks around for only a few minutes. If it were to be used as a drug, therefore, patients would have faced the unwelcome prospect of needing glp-1 injections every hour.

In 1990 John Eng, a researcher at the Veterans Affairs Medical Centre in The Bronx, discovered that exendin-4, a hormone found in the venom of the Gila monster, was similar to human glp-1. Crucially, the exendin-4 released after one of the monster’s rare meals is more resistant to enzymatic breakdown than glp-1, staying in its body for hours. It took more than a decade before exenatide, a synthetic version of the lizard hormone, created by Eli Lilly, an American pharma giant, and Amylin Pharmaceuticals, a biotech firm, was approved to treat diabetes in America. This breakthrough spurred other firms to develop more effective and longer-lasting glp-1 medications as a treatment option for diabetes, beyond injections of insulin.

Scientists had also been aware that glp-1 had another side-effect: it slowed the rate of “gastric emptying”, which allows food to stay in the stomach for longer and suppresses appetite. But the potential weight-loss benefits were not seriously pursued at first.